1. Field of the Invention
The present invention relates to a wireless modem, and more particularly, to a wireless modem system having a sleep mode applied thereto.
2. Description of the Related Art
Recently, with advancement of computer and communication technologies, a variety of wireless communication services provided using wireless communication networks are generalized. In addition to voice communication services provided through mobile communication terminals, the domain of the services is expanded even to multimedia communication services for transmitting circuit data, packet data and the like.
After the advent of Advanced Mobile Phone Systems (AMPS) of an analog cellular method categorized as a first generation mobile communication service and Global System for Mobile (GSM) and Code Division Multiple Access (CDMA) of a digital cellular method categorized as a second generation mobile communication service, International Mobile Telecommunication 2000 (IMT-2000) categorized as a third generation mobile communication service has been distributed recently.
Particularly, the IMT-2000 is classified into Wideband CDMA (WCDMA) of an asynchronous mode and CDMA-2000 of a synchronous mode. The WCDMA method is based on techniques related to wireless connection of a CDMA method and mobile communication networks of a GSM method, while the CDMA-2000 is based on techniques related to wireless connection and mobile communication networks of a CDMA method.
On the other hand, Wireless Broadband Internet (WiBro) service is a service for connecting to the Internet and using a variety of contents in a mobile environment of indoor and outdoor walking speed or medium-or-low speed using a portable mobile communication terminal.
Currently, wireless communication networks of a CDMA method are constructed throughout the nation, whereas wireless communication networks for WiBro services are limitedly constructed in some areas. Accordingly, in order to use both of the wireless communication networks, a wireless modem is driven by the following two methods.
First, the first method is to connect two USB type wireless modems for a personal computer (PC), which respectively support both of the communication networks, and simultaneously drive the wireless modems. Next, the second method is to drive a WiBro modem if a PC enters an area where WiBro services are provided and to drive a CDMA modem if the PC deviates from the area. Electrical current consumed when the first method is used and a driving time of a wireless modem when the second method is used are shown in FIGS. 1 and 2, respectively.
FIG. 1 is a view comparing electrical currents used when both of USB type WiBro and CDMA modems of a related art are connected to a PC and simultaneously driven. As shown in FIG. 1, when both of the WiBro and CDMA modems are connected and driven, input current flowing through a USB port of the PC exceeds the power limit of 500 mA of a USB interface if a communication network is connected through the CDMA modem.
FIG. 2 is a view showing a driving time required when a conventional USB type modem is connected to a PC and driven. As shown in FIG. 2, it takes more than 10 seconds until the USB type modem is connected to the PC and connects to a communication network from a power off state.
However, the above prior art has the following problems.
That is, if two of the wireless modems are simultaneously driven, there is a problem in that power limit of the USB interface limited to 500 mA is exceeded and thus breakdown of the PC may be invited. Particularly, since further higher power is used to be provided with Internet services in an area where radio wave reception strength is weak, the PC is further highly probable to be broken down due to excess of the power limit of the USB interface if the two wireless modems are simultaneously driven.
Furthermore, if the two modems are alternatively driven whenever the PC deviates from or enters a WiBro service area, there is a problem in that an extended booting time is required to register the location of the two wireless modems into respective communication networks.